A low temperature test chamber is needed to test cryogenic devices or circuits such as superconducting microwave devices. By low temperature is meant temperatures less than about 100.degree. K. Prior art cryogenic test chambers employ vacuum chambers. Vacuum chambers are expensive and great care and special fixtures are required to maintain the vacuum. Changing samples is very time consuming since the vacuum must be released and then reestablished when a test sample is replaced. The interior volume of a vacuum cryogenic test chamber is also limited to reduce the above problems, thus limiting the size of the test circuit which can be received by the chamber.